Effects of Roadway on Driver Stress: An On-Road Study using Physiological Measures

Abstract

There has been a great deal of research expended on enhancing our roadway to ensure that road users are provided a smoother, more enjoyable ride. One area that has not been well examined is the relationship to safety and stress. Human factors research shows that driver stress is associated with workload and fatigue, and is constructs that can have an impact on overall driver safety. The goal of this study was to examine whether there are different levels of driver stress across various roadway conditions. This goal is achieved using data collected from an on-road study with 60 drivers from three age groups (less than 25 years old, 35-55, and 65 and older). Physiological measurements associated with driver heart activity (ECG) were recorded and used as an indicator for cognitive workload. Patterns in stress responses were evaluated across age and gender for inverse trip sets along a pre-defined route. A heart rate variability (HRV) analysis was performed and both time and frequency domain parameters were examined. Short interval stress was used to assess trends in stress by distance traveled. Longer intervals were used to reflect induced stress from roadway characteristics. It was determined that the HRV parameters in conjunction with each other are stable indicators of mental workload. Similar responses were observed across all genders and ages, however the older age group had the largest incremental changes in physiological responses. Evidence suggests that drivers experienced increased cognitive demand along rough pavements (verified through IRI values) and through tunneled roadway segments. It was also conclusive that the route was short enough that fatigue induced by long duration driving was not significantly captured and thus the clockwise and counterclockwise data sets could be compiled into a singular HRV analysis.